Process for making non-woven batt



Sept. 8, 1964 w. T. ALLMAN, JR., ETAL 3,148,101

PROCESS FOR MAKING NON-WOVEN BATT 2 Sheets-Sheet 1 Filed June 26, 1958Sept; 8, 1964 w. T. ALLMAN, JR., ET AL 3,148,101

PRocEss Foa MAKING NoNwovEN BATT Filed June 26, 1958 2 Sheets-Sheet 2FIG.4. FIG.5.

United States Patent Ofi lice 3,l458,ll Patented Sept. 8, 1964 PROCESSFR The present invention relates to novel filters particularly suitedfor filtration of tobacco smoke, intermediates therefor, and processesof making such filters and i11- termediates.

Most cigarette filters of point the filaments may, and preferably do,deviate from the general longitudinal direction, i.e. the filaments arecrimped. In production of filters from such materials, prior to wrappingwith paper, it is necessary to form the bundle or tow of filaments, tocrimp the bundle, and then to store the crimped filaments because thelinear speed of subsequent processing differs from these earlier steps.It is then necessary to work or open the bundle or tow to separate theindividual filaments so that their crimps will be de-registered in ordernot to provide channels through which smoke will pass without beingfiltered, and to plasticize the opened tow to assist cohesion of thefilaments into a firm body. Following wrapping with paper the filtersmust be cured to cause the lament to adhere at points of contact and tostiften the filters.

It is an object of the present invention to provide a novel non-wovenbatt which can be manufactured easily and inexpensively, and which issuited for use in making filters for tobacco smoke.

Another object of the invention is to produce novel non-woven battsusing the same filament extrusion equipment generally used in spinningyarns.

Yet another object of the invention is to provide a cigarette filter ofimproved efiiciency, of reduced weight, and of high whiteness evenwithout added pigment.

A further object of the invention is to provide novel procedures forproducing cigarette filters which perform as Well as or better thanexisting filters.

Still :another object of the invention is to provide novel ltermaterials free of plasticizer and/or adhesives, composed exclusively offilamentary material.

Other objects and advantages will become apparent from the followingdetailed description and claims.

In accordance with one aspect of the present invention filament formingmaterial in liquid phase, e.g. in solution, is extruded through aplurality of orifices in the form of substantially parallel filamentsand the individual filaments are caused to be moved about relative toone another so as to contact each other while still plastic and tocoalesce or fuse at randomly spaced points, thereby forming a randomnon-woven batt. The batt is drawn away from the point of extrusion at alinear speed considerably slower than the linear speed at which thefilament forming material is extruded through the orifices so that theweight of the batt per unit length will be considerably greater than ifthe filaments were withdrawn at the same linear speed at which they wereextruded. The exact rate of withdrawal will depend upon the number oforifices, the speed of extrusion and the desired denier of the batt,i.e. the desired weight in grams of 9000 meters of the batt. This denierwill depend upon the end use contemplated for the batt; when it isintended to be used for manufacturing filters for cigarettes ofconventional size, e.g. about 25 mm. in circumference,

the denier of the whole batt generally ranges from about 40,000 to500,000 and preferably 55,000 to 100,000. Generally, the speed ofextrusion of the filaments will be at least about times, and preferablyat least about 400 times, the rate of withdrawal of the batt, althoughas noted the exact ratio may be varied widely depending on the otherconditions of operation.

The preferred batts generally have a thickness of at least about 5 mm.,e.g., 10 mm. to 50 mm., and a width of at least about 25 mm., e.g. about50 mm. to 300 mm. The apparent density of the batt as measured with asubstantially uncompressed sample is generally less than 2 pounds percubic foot and preferably less than l pound per cubic foot.

The dried batt can be rolled up or it can be given a small twist so asto form a rope of approximately cylindrical configuration. In either ofthese instances, or preferably directly as withdrawn in the form of anon-woven batt of randomly directed filaments, the mass is passedthrough a trumpet which reduces it to a cross section corresponding insize and shape to the cigarettes into which filters are to beincorporated. The continuously moving, approximately cylindrical rope isthen processed into cigarette filters in generally the same manner thata conventional opened and plasticized tow is processed, e.g. it may becontinuously wrapped in paper, cut into predetermined lengths and eitherpackaged for subsequent incorporation into cigarettes as the lterelements thereof or directly incorporated into cigarettes, except thatcuring is not necessary.

The characteristics of the non-woven batt and the performance ofcigarette filters produced therefrom will be largely dependent upon theconditions of extrusion. For example, the filaments when they contacteach other should still be sufficiently plastic to coalesce; on theother hand, it not sufficiently dry when they contact each other and aredeposited on the support, they will mat down and form a thin relativelydense batt which is less suited for cigarette filter production althoughit may have other uses.

Examples of filament forming materials are organic derivatives ofcellulose such as ethers and/ or esters thereof, e,g. ethyl cellulose,cellulose acetate, cellulose propionate, cellulose butyrate, celluloseacetate formate, cellulose acetate propionate, cellulose acetatebutyrate, etc., which esters may be ripened so as to modify theirsolubility characteristics or may be unripened, i.e. containing fewerthan about 0.29 free hydroxyl groups per anhydroglucose unit, such ascellulose triacetate. While other filament forming materials such apolyamides, e.g. nylon 6 or 66, linear polyesters such as polyethyleneterephthalate, acrylonitrile polymers and copolymers, oleiinic polymerssuc has polyethylene, polypropylene, polyvinyl chloride, polyvinylacetate, polyvinyl chloridevinyl acetate, polyvinylidene chloride, andthe like, can be employed, organic acid esters of cellulose, such ascellulose acetate, are preferred and these are advantageously extrudedas a solution into a heated evaporative atmosphere.

The invention will be more fully described with reference to theaccompanying drawing, wherein:

FIG, 1 is a schematic perspective View of an apparatus for formingcigarette filters in accordance with the invention;

FIG. 2 is a perspective view of a portion of a cigarette,

with the papers shown in section, having incorporated therein the filterof FIG. 1;

FIG. 3 is a plan view on an enlarged scale of the batt 24 formed in FIG.1; and

FIGS. 4, 5, 6, and 7 are photomicrographs of lengths of individualfilaments of the batt of FIG. 3.

Referring now more particularly to the drawing, in

FIG. l there is shown a closed cabinet 11 (with the front removed sothat the inside is visible) housing an endless highly porous member suchas a wire screen 12 trained about shafts 13, 14, at least one of whichis rotated, at relatively low speed, so that the top of screen 12 movesto the right. Hot air is admitted to the cabinet 11 at 15 and vaporsleave through pipe 16.

A solution of a filament forming material dissolved in a volatilesolvent is supplied by a conduit 1'7 to a multiorificed spinnerette orjet 18 through which it is extruded under pressure, in the same manneras when spinning yarn, as a plurality of substantially parallelfilaments 19 directed toward moving screen 12. inclined pipes 20 and 21are positioned in front of and behind the plane of the filaments 19,i.e. to the right and left of said plane, and direct jets of fluid, e.g.compressed air, fore and aft at the filaments 19 before they reachscreen 12 and cause the filaments to be drawn, i.e. to be reduced indenier, and to swirl about in a turbulent zone, each filament whippingabout and forming entanglements with itself and with other filaments.The solvent in filaments 19 starts evaporating upon contact with the hotair in cabinet 11 but the filaments 19 are still sufficiently Wet andplastic when acted upon by the air blasts from pipes 2f), 21 so thatthey occasionally fuse where they come in contact and are distorted intovaried geometrical configurations which are set by the rapid drying as aresult of the air blast. A pair of lateral baffles 22, 23 (the latterbeing shown partly broken away) are positioned above screen 12 anddetermine the Width of the batt 24 which forms as the entangledfilaments 19 drop to the screen. These baffles also serve to preventformation of a batt having lateral edges of lesser thickness or heightthan the middle, i.e. they aid in producing a uniform batt.

As noted, the blasts of air through pipes 20, 21 also serve to dry thefilaments 19 so that the batt 24 is almost fully dry after moving only ashort distance toward end wall 2S of cabinet 11. The batt 24 accordinglydoes not mat down but rather is lofty and of low density. The batt iscarried along by screen 12 and leaves cabinet 11 through an elongatedslit 26 in end Wall 25.

Batt 24 then enters the wide end of a trumpet 27 and is compactedlaterally therein and changed in cross section from a wide rectangle toan approximately cylindrical rope 28 of the approximate cross-sectionalshape and size of a cigarette. Rope 23 enters a paper wrapping apparatus29 along with paper 30 and an endless belt 31, the paper 30 beingwrapped about rope 28 and glued in apparatus 29 in conventional manner.`The wrapped rope 32 issuing from apparatus Z9 is then cut by knife 33into filter plugs 34 of predetermined length.

The plugs 34 are incorporated as the filters in cigarettes inconventional manner. As shown in FIG. 2, the plug 34 comprising aportion of rope 28 and paper 3ft is wrapped together with cigarettetobacco 3S in an outer paper 36 to form a filter-tipped cigarette 3'7.

As can be seen in FIG. 3 the batt 24 is an entangled mass ofsubstantially continuous substantially randomly directed filaments 19which are adhered to each other at spaced points so as not to be capableof being individually pulled out, although the individual filamentidentity is apparent over short distances. The edges of the batt 24, areof substantially the same thickness as the middle of the batt. Theagitation and turbulence produced by the air blasts produce the randomstructure as well as many small neps or clusters 38 which appear to becomposed of tight coils, knots, or entanglements of one or morefilaments. It has been observed that filters made from batts having suchneps exhibit greater filtration efiiciences.

The batt and filters produced therefrom are characterized by extremeuniformity, individual filters produced from different portions alongthe length of a given batt having substantially the same weights perunit length, the same filtration efiiciences, porosity, etc. The filterscompare extremely favorably, in both cost and performance,

with conventional filters. While a plasticizer may be used, it is notnecessary, and the plugs are of satisfactory firmness and resilience.They are also of excellent Whiteness, although no pigment has beenincorporated. The Weight of the novel filter, per unit length, is lessthan that of conventional filters of equal filtration efficiency.

In place of an elongated spinnerette as shown, a conventionalspinnerette with orifices arranged in a circular pattern may beemployed; several spinnerettes may be lined up transversely of thecabinet 11 to form a nonwoven batt of greater width (the baffles 22 and23, if present, being spaced further apart) or they may be lined up inlongitudinal direction of the cabinet to form a laminated batt ofgreater height or thickness. If desired, subdivided absorbents such assilica gel, fiber fioc, or the like can be deposited on the batt 24 incabinet 11 shortly after its formation and thus may be embedded in thebatt; if introduced before the batt is dry such additives may even beheld adhesively within the batt. In addition to use in making cigarettefilters, the batt can be used in spread condition for making fiatfilters or other articles generally prepared from non-wovens.

The number and disposition of the air blasts can be varied as desired tomodify the physical properties of the resulting batt.

Depending upon the temperature of the air in the cabinet and theconditions of extrusion, it is possible t0 practice the inventionwithout moving the screen 12, i.e. the batt immediately upon dropping tothe screen will be sufficiently coherent to be moved over the stationaryscreen without being disrupted. In place of a screen as support for thebatt, a plurality of parallel spaced filaments or yarns from a metier ora supply package can move beneath the spinnerette and can be joined tothe batt as a reinforcement. If the entangled mass is sufficientlycoherent as formed a support can be entirely omitted.

In the event that the denier of the batt 24 is greater than that desiredin the filters, the denier may -be reduced by speeding up the support orby drafting prior to condensing the batt in trumpet 27, eg. |by passingthe batt between a plurality of pairs of rolls successively moving atgreater peripheral speed. The resulting denier of the batt will be theproduct of the original denier and the peripheral speed of the firstpair of rolls divided by the peripheral speed of the last pair of rolls.

In accordance with another aspect of the invention, it has been foundthat more coherent batts and superior filters are produced when thefilaments are extruded under extremely high pressures. Desirably theextrusion pressure exceeds 600 p.s.i.g., which can be attained byemploying small orifices, eg. round orifices about .040 mm. or less indiameter with linear rates of extrusion of 700 or more meters perminute. Under such conditions the solvent appears to flash off andproduces filaments having surface characteristics different from thosegenerally resulting from dry spinning a solution through round orifices.Specifically, as shown in FIG. 4, a length of an individual filament 39is twisted about itself to form a loop 40. On a more highly magnifiedscale as shown in FIG. 5, the filament 39 has a ribbon-like rugosesurface with helical striations 41. FIG. 6 shows another filament 42having a longitudinal fold 43 and substantially parallel circumferentialstriations 44. These are shown on a less highly magnified scale in FIG.7. The folds 43 differ in height and their Width varies from aboutone-tenth to one-third of the fiber width. Their surfaces are slightlyindented. Some bifurcate into two divergent folds. The folds may be wellseparated or almost touch; in some areas they are very irregular andappear crumpled. lf any one fiber is examined through a small part ofits length, all or only some of these features may be observed.

As would be expected from the elevational views of the filaments, incross section they are irregular and have many lobes and deepindentations. In general, the filaments 19 have a rough crenulatedsurface which resembles the =bark of a tree. As a result of thesfriations and the knots there is more surface for a given weight offilament. The pits and irregularities increase the entrapment of smokeparticles when used as a filter and the irregularities produce a lockingaction which resists relative displacement of the filaments so that astronger more firm filter plug is produced.

Example Using the apparatus shown in the drawing, a 26.8% by weightsolution of cellulose acetate, acetyl value of 55%, in acetone isextruded through a jet having 30 circular holes, each .034 mm. indiameter, at a linear speed of about 1850 meters per minute (ie. at atotal volume of 50 ml. of solution per minute). The extrusion pressureis 1500 p.s.i.g. The temperature of the solution is 88 C. Air iswithdrawn at a temperature of 75 C. after being admitted to the cabinetat a temperature of 80 C. The screen 12 is positioned 20 cm. below thespinneret-te and advances at a speed of 1.75 meters per minute. Thelower ends of baffles 22, 23 are spaced 4.5 inches apart. Pipes 20 and21. terminate in wing tips which direct sheets of air at 20 p.s.i.g. and25 C. at approximately 45 angles with the vertical, the pipes beingpositioned so that the air blasts impinge upon the filaments and producea turbulent zone about 15 cm. below the face of the spinnerette. Theresulting bat is about 1 cm. thick and has a denier of 57,000. Asformed, it is fed into a filter making apparatus and converted intopaper wrapped filter plugs 15 mm. long and 25 mm. in circumference. Thecellulose acetate in each plug weighs 102 milligrams. It is tested onconventional filter testing equipment to determine the amount of suctionneeded to draw a predetermined volume of air therethrough under fixedconditions and to determine the percentage of solids removed from thesmoke produced by smoking cigarette tobacco. Fore ease of comparison theresults are tabulated below along with those for plugs of two of themost effective filter cigarettes commercially available:

From this tabulation it can be seen that the novel plugs have a pressuredrop intermediate the controls, indicating a lack of parallelism in thefilter so that there is no channeling. The filtration efficiency of thenovel filter is about 20% greater than that of the better of thecontrols and 50% greater `than the other control; its weight is lessthan 85% than that of the shorter plug (of lower efficiency) and lessthan 60% than that of the more eflicient plug.

The individual filaments vary in denier, averaging between about 2.6 and3.2. Their cross sections are extremely irregular `due to their pits andcrenulations, and the cross section of a given filament variesconsiderably at different longitudinal locations along the filament. Ingeneral the average maximum width of each of these filaments is about 30microns while the average minimum width is about l microns.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be madetherein without departing from the spirit of our invention.

Having described our invention what we desire to secure by LettersPatent is:

1. The process which comprises extrudng a filament forming material inliquid phase through a plurality of orices to form substantiallyparallel filaments, agitating through a plurality said filaments whilestill in plastic and mutually adhesive condition whereby the filamentscontact one another randomly and are coalesced at randomly spaced pointsin the absence of any externally applied binder, and collecting saidcoalesced filaments in the form of a non-woven batt.

2. The process set forth in claim 1, wherein said filament formingmaterial comprises cellulose acetate.

3. The process set forth in claim 1, including the further step ofwithdrawing said batt from where formed at a linear speed sufficient toproduct a batt of at least about 40,000 denier.

4. The process set forth in claim 3, wherein the filament formingmaterial is extruded under a pressure in excess of 600 p.s.i.g.

5. The process which comprises extrudng a filament forming material inliquid phase through a plurality of orifices to form substantiallyparallel filaments, directing a jet of a gas against said filament whilestill in plastic and mutually adhesive condition whereby the filamentscontact one another randomly and are coalesced at randomly spaced pointsin the absence of any externally applied binder, and collecting saidcoalesced filaments in the form of a non-woven batt.

6. The process set forth in claim 5, including the step of laterallyconfining said jet of a gas and said batt to produce a batt ofpredetermined width.

7. The process which comprises extrudng a solution of a filament formingmaterial in a Volatile solvent through a plurality of orifices into anevaporative atmosphere to form substantially parallel filaments,directing a jet of a gas against said filaments while still in plasticand mutually adhesive condition whereby the filaments contact oneanother randomly and are coalesced at randomly spaced points in theabsence of any externally applied binder, and collecting said coalescedfilaments in the form of a non-woven batt.

8. The process set forth in claim 7, wherein said solution comprisescellulose acetate dissolved in acetone.

9. The process set forth in claim 7 wherein said nonwoven batt iscollected on a porous support, and moving said support at a linear speedsufiicient to produce a batt of at least about 40,000 denier.

l0. The process which comprises extrudng a solution of a filamentforming material in a volatile solvent of orifices into a chamber toform substantially parallel filaments, continuously supplying air tosaid chamber and withdrawing air and solvent vapors therefrom, directinga jet of air against said filaments while still in plastic and mutuallyadhesive condition whereby the filaments contact one another randomlyand are coalesced at randomly spaced points in the absence of anyexternally applied binder, collecting said coalesced filaments in theform of a non-woven batt, and continuously withdrawing said non-wovenbatt from said chamber at a linear speed less than that at which thesolution was extruded through said orifices.

l1. The process which comprises extrudng under a pressure in excess of600 p.s.i.g. a solution of cellulose acetate in a volatile solventthrough a plurality of orifices into a chamber to form substantiallyparallel filaments, continuously supplying air to said chamber andwithdrawing air and solvent vapors therefrom, directing a jet of airagainst said filaments while still in plastic and mutually adhesivecondition whereby the filaments contact one another randomly and arecoalesced at randomly spaced points in the absence of any externallyapplied binder, collecting said coalesced filaments on a porous supportin the form of' a non-woven batt of predetermined width, and moving saidsupport at a linear speed sufficient to produce a batt of at least about40,000 denier.

12. The process which comprises extrudng a filament forming material inliquid phase through a plurality of orifices to form filaments,agitating said filaments while still in plastic and mutually adhesivecondition whereby the filaments contact one another randomly and arecoalesced at randomly spaced points in the absence of any externallyapplied binder, collecting said coalesced filaments in the form of anon-Woven batt, comprising said batt into a rope of the approximate sizeand crosssectional shape of a cigarette, and forming said rope intoiilters for cigarettes.

13. The process which comprises extruding a solution of a lament formingmaterial in a volatile solvent through a plurality of orifices into anevaporative atmosphere to form ilaments, directing a iet of Huid againstsaid filaments while still in plastic and mutually adhesive conditionwhereby the iiiaments contact one another randomly and are coalesced atrandomly spaced points in the absence of any externally applied binder,collecting said coalesced larnents in the form of a non-woven batthaving a denier of at least about 40,000, compressing said batt into arope of the approximate size and crosssectional shape of a cigarette,and forming said rope into iilters for cigarettes.

14, The process which comprises extruding under a pressure in excess of600 p,s.i.g. a solution of cellulose acetate in a volatile solventthrough a plurality of orifices into a chamber to form filaments,continuously supplying air to said chamber and withdrawing air andsolvent vapors therefrom, directing a jet of air against said lilamentswhile still in plastic and mutually adhesive condition whereby thefilaments contact one another randomly and are coalesced at randomlyspaced points in the absence of any externally applied binder,collecting said coalesced ilaments on a porous support in the form of anon-woven batt of predetermined width, moving said support at a linearspeed suicient to produce a batt of at least about 55,000 denier,compressing said batt into a rope of the approximate size andcross-sectional shape of a cigarette, and forming said rope into ltersfor cigarettes.

References Cited in the le of this patent UNITED STATES PATENTS2,242,988 Averns May 20, 1941 2,483,406 Francis Oct. 4, 1949 2,688,380MacHenry Sept. 7, 1954 2,707,308 Taylor et al. May 3, 1955 2,794,480Crawford et al June 4, 1957 2,795,290 Butsch et al, June 11, 19572,813,051 MacHenry Nov. 12, 1957 2,828,752 Jackson Apr. 1, 19582,884,681 Labino May 5, 1959 2,931,422 Long Apr. 5, 1960 2,988,469Watson `Tune 13, 1961 3,080,611 Jarrett et al Mar. l2, 1963

5. THE PROCESS WHICH COMPRISES EXTRUDING A FILAMENT FORMING MATERIAL INLIQUID PHASE THROUGH A PLURALITY OF ORIFICES TO FORM SUBSTANTIALLYPARALLEL FILAMENTS, DIRECTING A JET OF A GAS AGAINST SAID FILAMENT WHILESTILL IN PLASTIC AND MUTUALLY ADHESIVE CONDITION WHEREBY THE FILAMENTSCONTACT ONE ANOTHER RANDOMLY AND ARE COALESCED AT RANDOMLY SPACED POINTSIN THE ABSENCE OF ANY EXTERNALLY APPLIED BINDER, AND COLLECTING SAIDCOALESCED FILAMENTS IN THE FORM OF A NON-WOVEN BATT.